Photodegradation Mechanisms And Safety Evaluation Of Aflatoxin B₁ In Different Medias

The photodegradation behavior, products, pathway and mechanisms of AFB1 in different media were studied by the technique of UPLC-Q-TOF/MS in this article. The Ames test and cytotoxicity experiment were used here to evaluate the mutagenesis and toxicity of the photodegradation products of AFB1 in food, and an overall assessment of the safety of this detoxification method of Aflatoxins applied in peanut oil were carried out at last.Firstly, the photodegradation behavior at various initial concentration, wavelength, irradiation time and intensities were studied. The results indicate that the degradation ratio reduced at below order, v(UVA+UVC) > vUVC> vUVA , v800μw/cm2 > v400μw/cm2 >v200μw/cm2,vpeanut oil> vwater >vacetonitrile, and is not affected by the initial concentration, meanwhile AFB1 was proved to follow first-order reaction kinetics (R2≥0.9). At the same time, three photodegradation products A (C14H10O6), B (C17H14O6), D (C16H12O5) and the pathway of AFB1 in acetonitrile were identified using UPLC-Q-TOF/MS and elucidated by photochemistry mechanism. Hydrogen abstraction reaction of AFB1 lead to the generation of A, and then photoaddition at cite C(9c)-O(10) along with photoelimination reactions at cite C(6a)-C(9a) generated A product, at last the product D was generated by photoelimination at cite C(11)-O(15). Secondly, the photodegradation ratio and degradation products in various media were studied and discovered different in each media. The ratio in peanut oil is the fastest; in acetonitrile is the slowest, which was elucidated by the quantity of free electron in various medias.The degradation regular in water and peanut oil were verified the same to that in acetonitrile model, which follows the first-order reaction kinetics (R2≥0.9). Three photodegradation products P1 (C17H14O7), P2 (C16H14O6) and P3 (C16H12O7), which generated by photoaddition at cite C(8)-C(9) from AFB1 to P1, photoelimination at C(4)-O(12) and photoreduction reactions at O(1)-C(14) from P1 to P2 and photoelimination at C(12)-O(13) from P1 to P3, were identified and find that the main structures of them were similar to that of the AFB1. The possible photodegradation reaction in peanut oil was severe and the structure of AFB1 was destroyed thoroughly to minor molecular substances, such as R-COOH and R-CO-R'. The photodegradation pathway mechanism of AFB1 in two medias were elucidated seasonable by photochemistry principle.The Ames test was used to detect the mutagenesis of the photodegradation products in water and peanut oil. The results indicated that the reversion rate of the photodegradation in water (Pw) is higher than that of negative control (0ng AFB1), while there is no differences of the reversion rate between the photodegradation in oil (Po) and the negative control. The mutagenesis of the Pw decreased significantly but not be removed thoroughly, while that of Po is disappeared absolutely.MTT and FCM were employed to study the cytotoxicity of Pw, Po and AFB1 in HepG2 cell line. The results indicate that: the cell viability of AFB1-treated cell, used as positive control, decreas 78.6%. The cell viability of the Pw-treated cell reduce about 8.5%, while that of Po has no differences compared to the untreated cells, p>0.05. The expression of the antioncogene p53 protein in HepG2 cells treated by three tested compounds was detected by ELISA to evaluate the carcinogenicity of Po and Pw. The results showe that the expression of p53 protein significantly decrease in AFB1-treated cells; the concentration of p53 in Pw-treated cells slightly reduce and that in Po-treated cells has no difference compared with the untreated cells.The conclusion of the Ames test and the cytotoxicity are in agreement with the results of the identification of the photodegradation products in two kinds of media. The main structures of Pw are similar with the AFB1, and the furan ring, one of the toxic activity cites of AFB1 was not destroyed, remaining the corresponding toxicity. In contrast, the possible structures of Po are different from AFB1, following great change of the chemical nature, for that the corresponding toxicity and the carcinogenicity disappeared.At last, acidity value, iodine value, peroxide value, concentration of VE and total trans fatty acids as well as oil stability index were selected to study the effect of UV detoxification irradiation treatment on the quantity of peanut oil. The results show that there is no significant change of these parameters (p>0.05) except the significant increase of the peroxide value (p<0.01) after the selected dose (2ppm AFB1 can be destroyed absolutely) of UV irradiation treatment, which indicating that detoxification method used in peanut oil is not only effective, but also has no bad effect on the quantity of peanut oil.